Science and Issues

Oil Spills: Impact on the Ocean

Oil wastes that enter the ocean come from many sources, some being
accidental spills or leaks, and some being the results of chronic and
careless habits in the use of oil and oil products. Most waste oil in the
ocean consists of oily stormwater drainage from cities and farms,
untreated waste disposal from factories and industrial facilities, and
unregulated recreational boating.

It is estimated that approximately 706 million gallons of waste oil enter
the ocean every year, with over half coming from land drainage and waste
disposal; for example, from the improper disposal of used motor oil.
Offshore drilling and production operations and spills or leaks from ships
or tankers typically contribute less than 8 percent of the total. The
remainder comes from routine maintenance of ships (nearly 20 percent),
hydrocarbon
particles from onshore air pollution (about 13 percent), and natural
seepage from the seafloor (over 8 percent).

Prevalence during Drilling versus Transportation

Offshore oil spills or leaks may occur during various stages of well
drilling or workover and repair operations. These stages can occur while
oil is being produced from offshore wells, handled, and temporarily
stored; or when oil is being transported offshore, either by flowline,
underwater pipeline, or tanker. Of the approximately 706 million gallons
of waste oil in the ocean each year, offshore drilling operations
contribute about 2.1 percent, and transportation accidents (both ships
and tankers) account for another 5.2 percent. The amount of oil spilled
or leaked during offshore production operations is relatively
insignificant.

Oil waste from offshore drilling operations may come from disposal of
oil-based drilling fluid wastes, deck runoff water, flowline and
pipeline leaks, or well failures or blowouts. Disposal of offshore
production waste can also pollute the ocean, as can deck runoff water,
leaking storage tanks, flowline and pipeline leaks, and the wells
themselves. Oil spilled from ships and tankers includes the
transportation fuel used by the vessels themselves or their cargos, such
as crude oil, fuel oil, or heating oil.

Over half the ocean's waste oil comes from land-based
sources and from unregulated recreational boating. The heavy
development in this busy California port illustrates one potential
source of petroleum contamination in coastal waters. (Note dark
plume in left foreground.)

Oil Spill Behavior

When oil is spilled in the ocean, it initially spreads in the water
(primarily on the surface), depending on its relative density and
composition. The oil slick formed may remain cohesive, or may break up
in the case of rough seas. Waves, water currents, and wind force the oil
slick to drift over large areas, impacting the open ocean, coastal
areas, and marine and terrestrial habitats in the path of the drift.

Oil that contains
volatile organic compounds
partially evaporates, losing between 20 and 40 percent of its mass and
becoming denser and more viscous (i.e., more resistant to flow). A small
percentage of oil may dissolve in the water. The oil residue also can
disperse almost invisibly in the water or form a thick
mousse
with the water. Part of the oil waste may sink with suspended
particulate matter, and the remainder eventually congeals into sticky
tar balls. Over time, oil waste weathers (deteriorates) and
disintegrates by means of photolysis (decomposition by sunlight) and
biodegradation (decomposition due to microorganisms). The rate of
biodegradation depends on the availability of nutrients, oxygen, and
microorganisms, as well as temperature.

Oil Spill Interaction with Shoreline.

If oil waste reaches the shoreline or coast, it interacts with sediments
such as beach sand and gravel, rocks and boulders, vegetation, and
terrestrial habitats of both wildlife and humans, causing erosion as
well as
contamination
. Waves, water currents, and wind move the oil onto shore with the surf
and tide.

Crude oil from the
Sea Empress
tanker spill coats a beach at Pembrokeshire, Wales in 1996.
Although marine transportation accidents can result in such oil
spills, they account for only about 5 percent of the waste oil that
enters the ocean annually.

Beach sand and gravel saturated with oil may be unable to protect and
nurture normal vegetation and populations of the substrate
biomass
. Rocks and boulders coated with sticky residue interfere with
recreational uses of the shoreline and can be toxic to coastal wildlife.

Examples of Large Spills.

The largest accidental oil spill on record (Persian Gulf, 1991) put 240
million gallons of oil into the ocean near Kuwait and Saudi Arabia when
several tankers, port facilities, and storage tanks were destroyed
during war operations. The blowout of the
Ixtoc I
exploratory well offshore Mexico in 1979, the second largest accidental
oil spill, gushed 140 million gallons of oil into the Gulf of Mexico. By
comparison, the wreck of the
Exxon Valdez
tanker in 1989 spilled 11 million gallons of oil into Prince William
Sound offshore Alaska, and ranks fifty-third on the list of oil spills
involving more than 10 million gallons.

The number of large spills (over 206,500 gallons) averaged 24.1 per year
from 1970 to 1979, but decreased to 6.9 per year from 1990 through 2000.

Damage to Fisheries, Wildlife, and Recreation

Oil spills present the potential for enormous harm to deep ocean and
coastal fishing and fisheries. The immediate effects of toxic and
smothering oil waste may be mass
mortality
and contamination of fish and other food species, but long-term
ecological effects may be worse. Oil waste poisons the sensitive marine
and coastal organic substrate, interrupting the food chain on which fish
and sea creatures depend, and on which their reproductive success is
based. Commercial fishing enterprises may be affected permanently.

Wildlife other than fish and sea creatures, including mammals, reptiles,
amphibians, and birds that live in or near the ocean, are also poisoned
by oil waste. The hazards for wildlife include toxic effects of exposure
or ingestion, injuries such as smothering and deterioration of thermal
insulation, and damage to their reproductive systems and behaviors.
Long-term ecological effects that contaminate or destroy the marine
organic substrate and thereby interrupt the food chain are also harmful
to the wildlife, so species populations may change or disappear.

Coastal areas are usually thickly populated and attract many
recreational activities and related facilities that have been developed
for fishing, boating, snorkeling and scuba diving, swimming, nature
parks and preserves, beaches, and other resident and tourist
attractions. Oil waste that invades and pollutes these areas and
negatively affects human activities can have devastating and long-term
effects on the local economy and society. Property values for housing
tend to decrease, regional business activity declines, and future
investment is risky.

Long-term Fate of Oil on Shore

The fate of oil residues on shore depends on the spilled oil's
composition and properties, the volume of oil that reaches the shore,
the types of beach and coastal sediments and rocks contacted by the oil,
the impact of the oil on sensitive habitats and wildlife, weather
events, and seasonal and climatic conditions. Some oils evaporate,
disperse, emulsify, weather, and decompose more easily than others. The
weather and seasonal and climatic conditions may accelerate or delay
these processes.

In 2000, several thousand penguins were affected by a fuel oil
spill after the iron-ore carrier
Treasure
sank off South Africa. Many oil-soaked birds were cleaned and
released.

Oil waste that coalesces into a tar-like substance or that saturates
sediments above the surf and tide level is especially persistent.
Efforts to remove the oil and clean, decontaminate, and remediate an
oil-impacted shoreline may make the area more visibly attractive, but
may be more harmful than helpful in terms of actual recovery.

Cleanup and Recovery

The techniques used to clean up an oil spill depend on oil
characteristics and the type of environment involved; for example, open
ocean, coastal, or
wetland
. Pollution-control measures include containment and removal of the oil
(either by skimming, filtering, or
in situ
combustion), dispersing it into smaller droplets to limit immediate
surficial and wildlife damage, biodegradation (either natural or
assisted), and normal weathering processes. Individuals of large-sized
wildlife species are sometimes rescued and cleaned, but micro-sized
species are usually ignored.

Oil spill countermeasures to clean up and remove the oil are selected
and applied on the basis of many interrelated factors, including
ecological protection, socioeconomic effects, and health risk. It is
important to have contingency plans in place in order to deploy
pollution control personnel and equipment efficiently.

Environmental Recovery Rates.

The rate of recovery of the environment when an oil spill occurs depends
on factors such as oil composition and

Workers clean up an oil refinery spill that polluted Anacortes Bay,
Washington. The floating ring of absorbent pads trailing behind the
boat is being used to contain some of the oil that has spilled.

properties and the characteristics of the area impacted, as well as the
results of intervention and remediation. Physical removal of oil waste
and the cleaning and decontaminating of the area assist large-scale
recovery of the environment, but may be harmful to the substrate
biomass. Bioremediation efforts—adding microorganisms, nutrients,
and oxygen to the environment—can usually boost the rate of
biodegradation.

Because of the type of oil spilled and the Arctic environment in which
it spilled, it is estimated that the residue of the
Exxon Valdez
oil spill will be visible on the Alaskan coast for 30 years.

Costs and Prevention

The costs of an oil spill are both quantitative and qualitative.
Quantitative costs include loss of the oil, repair of physical
facilities, payment for cleaning up the spill and remediating the
environment, penalties assessed by regulatory agencies, and money paid
in insurance and legal claims. Qualitative costs of an oil spill include
the loss of pristine habitat and communities, as well as unknown
wildlife and human health effects from exposure to water and soil
pollution.

Prevention of oil spills has become a major priority; and of equal
importance, efforts to contain and remove oil that has spilled are
considered to be prevention of secondary spills. The costs associated
with oil spills and regulations governing offshore facilities and
operations have encouraged the development of improved technology for
spill prevention. The Oil Pollution Act of 1990 was enacted by the U.S.
Congress to strengthen oil spill prevention, planning, response, and
restoration efforts. Under its provisions, the Oil Spill Liability Trust
Fund provides cleanup funds for oil pollution incidents.

Responsibility for the prevention of oil spills falls upon individuals
as well as on governments and industries. Because the sources of oil
waste in
the ocean are generally careless, rather than accidental, truly
effective prevention of oil spills involves everyone.

RECOVERING FROM THE EXXON VALDEZ OIL SPILL

A large quantity of crude oil was deposited on beaches in Prince William
Sound and along the shoreline of the Gulf of Alaska after the
Exxon Valdez
tanker wrecked in 1989. The oil waste has been closely monitored to
determine its status and its effects in the ocean and along the coast.

Initial efforts to remove the oil from intertidal areas included
flushing them with hot water applied with high pressure, which proved
fatal for much of the marine life involved. Natural rates of
biodegradation and recovery have been slower than anticipated, and
visible residue may persist for up to 30 years.

Thanks for sharing this information with the people of the internet. It is very interesting to know what factors determine the effects of the oil spills in detail instead of just a simple cause and and effect to the cause.

Oil Spills can be cleaned by different methods. However the most important method for cleaning oil is using generations of microbes that can eat the oil.
In the case of present oil disaster from BP, US should use the sub-marines to suck the oil and send it to the surface of Gulf of Mexico to be sent it to the tankers and then to the storage.

I wonder why the media doesn't share this truthful information with the public on the hazards of a sea floor volcano gushing toxic hazardous fluids by the millions of gallons per day into the gulf of Mexico